Conserved regulators of mating are essential for Aspergillus fumigatus cleistothecium formation

Sexual reproduction of the human pathogen Aspergillus fumigatus (teleomorph: Neosartorya fumigata) was assumed to be absent or cryptic until recently, when fertile crosses among geographically restricted environmental isolates were described. Here, we provide evidence for mating, fruiting body development, and ascosporogenesis accompanied by genetic recombination between unrelated, clinical isolates of A. fumigatus, and this evidence demonstrates the generality and reproducibility of this long-time-undisclosed phase in the life cycle of this heterothallic fungus. Successful mating requires the presence of both mating-type idiomorphs MAT1-1 and MAT1-2, as does expression of genes encoding factors presumably involved in this process. Moreover, analysis of an A. fumigatus mutant deleted for the nsdD gene suggests a role of this conserved regulator of cleistothecium development in hyphal fusion and hence heterokaryon formation.